Yes this appears to be an alternative to get Neoliberalism, though you can get it with a market economy.

So, Liberal/Reformist doctrines + Limited Multiparty + Small Control + State Capitalism or Market Economy + below 50 Diplomatic Reputation, otherwise other liberal subsystem

I've found that with Neoliberalism you need the following:
Parties doctrine no more liberal than Limited Multiparty
Civil Rights doctrine no more liberal than Small Control
If the Economy doctrine is to the left of Mixed Economy then Diplomatic Reputation must be less than or equal to 50
All other doctrines should be as liberal as necessary for the other liberal subsystems

I didn't need Nowadays Worldview above 70 to get this

It's not impossible. I got it several times. It's easier with a Birdcage economy and keeping religious doctrines away from secularism.

I've been trying to get Eurocommunism, but it always switches to Social Democracy. Is there something I'm missing, is it just impossible to be Eurocommunist?

I think you just need conservative socialism and no stronghold, nationalism and diplomacy does not affect it

I've tried fulfilling your Leninism Doctrine recommendations with all Nowadays Worldview types, I even lowered the diplomatic reputation below 70 and joined CMEA and WTO to be sure and it still had Conservative Socialism as the Subsystem.

Now this is strange! I am certain Leninism is fully compatible with the Stronghold of Maoism modifier. Have you tried with cosmopolitanism as Nowadays Wolrdview?

Social Democracy is correct that you need to have social democracy/liberalism as the state system and have state capitalism/birds cage as the economy type, but it seems you need to have your diplomatic reputation to be at least 50 and a Nowadays Worldview below 70.

For Conservative Socialism you don't need a authoritarian party line. You just need to have Conservative Socialism as the state system without fulling the prerequisites for any other subsystem. E.g. I fulfilled the doctrine requirements for Leninism you recommended in one playthrough and it gave me Conservative Socialism as the subsystem because apparently I had not "debunked" Maoism to get rid of the stronghold of Maoism modifier and rehabilitated Wang Ming, furthermore the party line drifted to Harsh while the state system was Conservative Socialism the whole time.

Centrism is correct that you need to have social democracy/liberalism as the state system, but you can get it both through both a state capitalist and market economy depending on your diplomatic reputation and Nowadays Worldview. With a State capitalist economy your diplomatic reputation and Nowadays Worldview are both below 70. When you market economy your diplomatic needs to be above 70 and your Nowadays Worldview needs to be below 70.

Liberalism is correct that you need to have social democracy/liberalism state system, but you need to have a market economy and both your diplomatic reputation and Nowadays Worldview need to be below 70.

Neoliberalism is correct that you need to have social democracy/liberalism as your state system, but you need to have a market or state capitalist economy and your Nowadays Worldview needs to be above 70.

I have a few observations I'd like to contribute to the guide.